Runway Act-Two at 5 credits a second vs Kling motion control on Sume

Runway's developer pricing page lists Act-Two at 5 credits per second, and credits cost $0.01 each there, so $0.05 per second (read 2026-10-07). Sume's Kling 3.0 Motion Control route costs $0.1575 per second. Sume does not offer Act-Two, so the choice is between two different products, not two prices for one product.

Dollar-per-second is only the first filter. The two routes accept different inputs, and the cheaper one is only cheaper if its output fits your job.

The prices in dollars

Runway sells API credits at $0.01 each. The same page lists Gen-4.5 at 12 credits per second and Gen-4 Turbo at 5 credits per second. Sume bills the Kling list of $0.126 per second times 1.25.

What the two routes take

Runway's pricing page states a price for Act-Two but does not describe its inputs, so this post does not either. Read Runway's own guide for what a performance clip and a character must look like.

Sume's Kling route takes one still (an image_url or a ready avatar), a public HTTPS motion reference of up to 30 seconds, and a declared duration_seconds. A prompt only steers appearance. Motion, framing, and length come from the reference clip, and the clip's sound is kept unless you set keep_original_sound to false.

Why Kling shows up in both places

Runway's product updates for September 18 say Kling models were deployed, including 3.0 Motion Control (read 2026-10-07). Its developer pricing page does not list Kling models, so the dollar rate of Kling on Runway is not stated there and is not compared here. If you already use Runway for other models, that is a reason to stay; if you want one balance and one job API across video, image, and audio, Sume runs the Kling route directly.

How to decide

A 30-second Kling clip on Sume reserves $4.725. The same 30 seconds of Act-Two at the listed rate is $1.50. Run a 5-second test on each before you scale, because quality, not the rate, decides the real cost of a retake.

• Your job is a performance on camera mapped onto a character, and Act-Two fits your assets: test Act-Two at $0.05 per second.
• Your job is a still plus a movement clip, up to 30 seconds, with the reference sound kept: Kling motion control on Sume at $0.1575 per second.
• You need Sume job features such as an idempotency key, webhook mode, and refund on failure: those exist on the Sume route and are shown in the Python walkthrough.